head-on (Adjective) — Characterized by direct opposition. ex. "a head-on confrontation"
head-on (Adjective) — Meeting front to front. ex. "a head-on collision"
head-on (Adverb) — In direct opposition; directly. ex. "we must meet the problem head-on"
head-on (Adverb) — With the front foremost. ex. "the cars collided head-on"